1. Field of the Invention
Embodiments of the present invention relate to an apparatus and method for measuring an overall heat transfer coefficient, and more particularly, to an apparatus and method for measuring an overall heat transfer coefficient that may measure a heat-retaining performance of a covering material or a thermal screen more efficiently by sealing a case.
2. Description of the Related Art
A greenhouse refers to a facility in which a cultivation space isolated from outside weather is created by covering an area with glass or a plastic film. In the greenhouse, crops are produced by artificially adjusting environments, for example, micrometeorological conditions or internal medium conditions, using a variety of supplementary equipment.
In general, an actual greenhouse may be covered with an external covering material and an internal thermal screen to minimize an external loss of heat from the greenhouse and maintain growing environment conditions, for example, a desired temperature and humidity level of the greenhouse, to be suitable for growing crops.
Heat externally lost from such a greenhouse includes convective heat, radiant heat, and conductive heat.
The convective heat refers to a transfer of heat by a temperature difference between a solid surface and a fluid. The radiant heat refers to heat produced when heat emitted from a heat source of a relatively high-temperature object passes through a space and is absorbed into a relatively low-temperature object. The conductive heat refers to a transfer of thermal energy in a solid from relatively high temperature to relatively low temperature.
However, in practice, a loss of heat by night sky radiation cooling is relatively significant in a case of a greenhouse used for agriculture.
In view of such various effects, an overall heat transfer coefficient of a covering material or a thermal screen may be measured. In this regard, Korean Patent Application No. 10-2007-0070495, filed on Jul. 13, 2007, discloses “Device for calculating convective heat transfer coefficient and method thereof”.